Cross-Chain Bridge Exploits

Every bridge is the same promise in different code: lock value here, mint a claim there, and let a verifier swear the two match. The verifier is the entire security model, and it is usually the least reviewed component in the stack.

How this vector actually works

The exploits collected here are failures of proof, not of cryptography — a message accepted without validation, a DVN that signed what it should have refused, a router that trusted its caller. Each case shows the exact line where the promise stopped being enforced.

  • Lock and mint — Collateral sits on chain A. Chain B mints a representation of it. Solvency depends entirely on the two staying in sync.
  • The verification gap — A forged message, a quorum that can be reached alone, or a missing check lets chain B mint without chain A ever locking.
  • The cash-out — The phantom asset is swapped against real liquidity within minutes, then bridged onward before governance can pause anything.

Red flags you can check in a minute

Any single item below is enough to stop and verify before you sign, send or install anything. Real collateral on one side, a claim on the other. When verification breaks, the claim wins.

  • The bridge's verifier set is small, permissioned, or run by the same team as the bridge.
  • Upgrade keys are a single multisig with a low threshold and no timelock.
  • Total value locked greatly exceeds the size of the last audit's scope.
  • Wrapped supply on the destination chain has drifted from locked collateral.
  • Incident communications arrive hours after on-chain sleuths already published.

If it already happened

Order matters more than speed of panic: contain the wallet first, preserve the evidence second, report third. Recovery services that contact you after the fact are the follow-up scam.

  • Exit wrapped positions before the peg follows the news — depegs are fast.
  • Withdraw approvals to the bridge router; exploited routers are re-used.
  • Track the official post-mortem for a reimbursement snapshot block, and keep proof of your position at that block.
  • Do not trust 'recovery portals' announced in replies — they are the second wave of the same attack.

Related vectors and tools

Most real cases mix two vectors, so read the neighbouring hubs, and run anything suspicious through the detector before you act on it.